Model test of composite anchorage bearing capacity on rock foundation

Objective The bearing capacity of anchorage with notched sill has traditionally been considered to rely primarily on its self-weight and base friction, yet the determination of its critical burial depth and the synergistic enhancement mechanism from pile addition remain unclear. Therefore, this study aims to systematically reveal the influences of burial depth and pile addition on its bearing capacity and anti-sliding mechanism. Method Relying on the notched sill anchorage project of a certain super-large bridge built on rock foundation, a similarity ratio of 1∶100 was adopted. According to the similarity theory and dimensional analysis principles, the similarity relations among various physical quantities were derived. A laboratory loading test device for gravity anchorage was independently designed, and the step loading was controlled through a hydraulic servo system. On this basis, four physical model tests were conducted in the same test conditions, i.e., shallow burial depth without piles (QW model), shallow burial depth with piles (QY model), deep burial depth without piles (SW model), and deep burial depth with piles (SY model). In different burial depths and with or without pile addition conditions, the displacement-load relation curves of anchorage, the distribution characteristics of foundation strain, and the deformation and stress rule of pile body were analyzed. Result The ultimate bearing capacities of four anchorage models are 4P (QW model), 7 P (QY model), 7 P (SW model) and 8 P (SY model) respectively, where P is the design value of cable tensile force. Increasing the burial depth of anchorage or adding piles can both significanty improve the ultimate bearing capacity of anchorage, improving by 3P. Compared with the condition of deep burial with adding piles, adding piles in shallow burial condition is easier to exert the bearing capacity of piles. Moreover, the shallow burial anchorage is more economical. In the pile addition conditions, i.e., QY model and SY model, the deep position of foundation is mobilized first, and the rate of strain increases gradually after the pile deformation reaches a certain degree. The front row piles mainly bear pressure, while the rear row piles mainly bear uplift resistance. The middle row piles bear relatively small loads; and their capacities are gradually utilized only after the bearing capacity of rear row piles are fully utilized. Conclusion This study provides clear guidance for design optimization of gravity anchorage on rock foundations, significantly improving economic efficiency while ensuring engineering safety. It is of good reference value for promoting bridge engineering to environmentally friendly and sustainable direction.